Brachytherapy system for prostate cancer treatment with computer implemented systems and processes to facilitate pre-implantation planning and post-implantation evaluations with storage of multiple plan variations for a single patient

ABSTRACT

A system for assisting a user in preparing a brachytherapy pre-implantation plan and post-implantation evaluation for prostate cancer is disclosed. Image scans are loaded into the system. The user places seeds on the various image scans to treat the prostate cancer. The system of the present invention provides for creation of multiple variations to allow a user to compare and contrast plans or evaluations. A user can more easily move between variations of an original plan or evaluation, thereby simplifying the plan and evaluating process. Creation of multiple variations will depend upon altering certain user defined variables.

PRIORITY

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/076,226, filed Feb. 27, 1998.

FIELD OF THE INVENTION

[0002] The invention relates to computer implemented systems andprocesses to facilitate pre-implantation planning and post-implantationevaluations of image-guided brachytherapy procedures for treatment ofprostate cancer.

BACKGROUND OF THE INVENTION

[0003] Brachytherapy procedures for treatment of prostate cancer arewell known. Brachytherapy involves treating cancer by precisely locatinga plurality of radiation sources (e.g., pellets of a radioactive isotopeor “seeds”) inside a human body in a three-dimensional array. Smallamounts of a radioactive isotope, such as iodine-125 or palladium-103,are encapsulated in a suitable casing to form the seeds which areimplanted. The seeds are placed in the treatment area according to aseed placement plan.

[0004] At least four major steps are performed in a brachytherapyprocedure for the treatment of prostate cancer using a perineal approachto the prostate guided by, for example, transrectal ultrasonography.First, a transrectal ultrasound study or other suitable imagingtechnique is used to gain information concerning the location, size andpositioning of a patient's prostate, surrounding tissues and surroundingorgans. The imaging of the structures may be in the form of a visualimage on a suitable medium or in the form of electronic data. In theformer case the image may be captured as, for example, an ultrasoundfilm or ultrasound Poloroid® scan which is then digitized by manuallyoutlining the desired features. In the latter case, for example, rawultrasound data may be captured and stored in electronic format.Ultrasound data may also be in the form of a VCR tape of an ultrasoundstudy.

[0005] Second, a pre-implantation seed placement plan is developed todetermine the desired location of the seeds in a three-dimensionalspace. A goal of the seed placement plan is to enable sufficient dosesof radiation to impinge on the target structures or portions ofstructures needing treatment, while minimizing radiation to otherstructures or portions of structures in and near the treatment area,such as healthy tissue of the adjacent rectum and bladder. Generalcriteria for establishing seed placement plans is known. In general, theprocess of generating a seed placement plan involves proposing thelocation of a plurality of seeds in a three-dimensional space, and,based on the known radiation characteristics of the seeds, calculatingthe radiation dose levels within the treatment area resulting from theproposed seed placement. The effectiveness of the proposed plan mayconveniently be determined through the use of isodose lines which may bedisplayed for the user. Various revisions to the plan and reevaluationmay be made in an attempt to optimize the plan. Each iteration ofrevisions to the plan and reevaluation is time consuming since itrequires recalculation of the dosimetry and the expected results foreach proposed placement plan.

[0006] Once an acceptable plan is developed the third step is tophysically implant the seeds according to the optimized seed placementplan and using known brachytherapy protocols. The seeds are typicallydelivered and positioned using needles which are inserted through acatheter or microcatheter. One method of increasing the accuracy ofplacement involves placing a needle guide template over the perineum toassist the physician in placing the seeds in the patient's prostate. Theneedle guide template is a physical device of knot geometry containingholes with predetermined (e.g., half-centimeter) spacing. The needleguide template may be registered by identifying two known landmarks in acaptured image and accounting for any relative translation, rotation, orscaling of the image.

[0007] The last major step in the procedure may include a post-implantevaluation procedure. In this step, the actual location of the seeds isdetermined and compared with the intended seed location as specified inthe seed placement plan. To do this, post-implementation images of thetreatment area are taken, so that the actual location of each seed canbe identified. Imaging techniques which are distinct from those used forpre-implantation are typically used during the post-implantation phase.After obtaining the post-implantation imaging, a comparison of eachseed's planned location with its actual location may be made. Ifnecessary, further implantation may be performed or the previousimplantation locations may be adjusted according to medically knownprocedures.

[0008] Computer implemented systems for assisting with some or all ofthe above steps are known. Software for one such system is availablefrom Multimedia Medical Systems, the assignee of the present invention,and others. One such system is marketed by the assignee as MMSTherpacPLUS™ Version 6.5. These known systems are useful in assistingwith certain aspects of the pre-implantation plan and thepost-implantation evaluation, but have various limitations anddrawbacks.

[0009] While known systems are generally effective in developing andimplementing a seed placement plan according to the specific aspects ofeach patient's physiological makeup, they are often deficient when it isnecessary or desirable to develop multiple, alternative seed placementplans and work with them over time until the most beneficial plan isselected for implementation. This is especially true in connection withcomplex placement plans that require multiple iterations to optimize. Inparticular, known systems do not typically permit user-friendly andefficient evaluation, storage and selection between and among multipleseed placement plans.

SUMMARY OF THE INVENTION

[0010] An object of the invention is to overcome the limitations anddrawbacks of prior systems.

[0011] Another object of the invention is to provide a computerimplemented system and process for facilitating seed placement planningand post-implantation evaluations wherein multiple variations of suchplans and evaluations are easily accessible and may be compared againstone another.

[0012] Another object of the invention is to permit access to andmanipulation of seed placement plans and post-implantation evaluationsin a user-friendly and efficient manner.

[0013] According to one aspect of the invention, multiple variations ofpre-implantation seed placement plans and post-implantation evaluationsmay be simultaneously created, stored, retrieved and manipulated. Eachvariation may contain one or more distinctions from other variations.The variations are stored in the system and may be compared against oneanother in order to systematically select the most beneficial plan ordetermine the most likely effect of implantation following theimplantation procedure.

[0014] These and other objects, aspects, and features of the presentinvention shall become apparent from the accompanying figures and thedetailed description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a block diagram of the brachytherapy pre-implantationplanning and post-implantation evaluating system.

[0016]FIG. 2 is a flow chart of the pre-implantation planning of oneembodiment of the invention.

[0017]FIG. 3 is an example of a graphical user interface thatillustrates various aspects of seed placement or identification in oneembodiment of the invention.

[0018]FIG. 4 is a flow chart of the post-implantation evaluation processof one embodiment of the present invention.

[0019]FIG. 5 is an example of a graphical user interface thatillustrates various aspects of seed identification in apost-implantation evaluation.

[0020]FIG. 6 is an example of a graphical user interface whichillustrates a pull-down menu presented to a user to operate variationsof a post-implantation evaluation.

[0021]FIG. 7 is an example of a graphical user interface whichillustrates a dialog box presented to a user to create variations of apost-implantation evaluation.

[0022]FIG. 8 is an example of a graphical user interface whichillustrates a dialog box presented to a user to rename variations of apost-implantation evaluation.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[0023] In order to illustrate the multiple variations of plans availablefor comparison and selection in connection with the pre-implantation andpost-implantation steps, it is useful to briefly describe thepre-implantation planing steps and the post-implantation steps.

[0024]FIG. 1 is a schematic block diagram depicting an example of abrachytherapy pre-implantation planning and post-implantation evaluatingsystem 100 according to one embodiment the present invention. As shown,system 100 may comprise a processor 310, an input device 320, userinterface device 350, a display device 330, data storage device 360 anda printer 340. Processor 30 may be a personal computer running anoperating system such as Microsoft Windows 95 or Microsoft Windows NT.Some or all of the steps associated with the present invention may beimplemented through application software resident on system 100. Inputdevice 320 loads image scans from an imaging device, such as anultrasound or computerized tomography (CT) scan device, into system 100such that the image is stored electronically in data storage 360. Inputdevice 320 may be, for example, an optical scanner. In a preferredembodiment of the invention, input device 320 comprises a digitizer fromthe AccuGrid line of digitizer tablets available from the NumonicsCorporation or another similar digitizer. Images may be catalogued,stored and retrieved using an appropriate document management system orthrough operating system software.

[0025] A user of system 100 may view the image scans on display device330 once they are loaded into system 100. Additionally the user mayemploy system 100 to manipulate the image scans as desired throughcommands entered at user interface device 350 which may be a keyboard,mouse, joystick, touchscreen, any combination of the above or othersuitable input device. The user may print out image scans and other dataresident on system 100 using printer 340.

[0026] System 100 directs a user through a series of steps in designinga pre-implantation brachytherapy plan, as illustrated by the flowchartof FIG. 2. Preferably. the user is stepped through the process via agraphical user interface generated by processor 310 and displayed ondisplay device 330. The user enters commands and controls the processthrough the use of user interface device 350. System 100 begins at step10 in performing a pre-implantation plan and loads pre-implantation dataat step 12. During this step, the pre-implementation image scansassociated with the selected patient are loaded. The image scans may beacquired through various techniques. For example, some techniques mayinclude direct video capture from an ultrasound device or a video tapeof the procedure, transmission and acquisition using DICOM (DigitalImaging and Communications in Medicine) standard data, or magneticdigitization (e.g., using a backlit magnetic digitizer tablet, similarto digitizer tablets used for CAD/CAM applications).

[0027] In addition to imaging data, pre-implantation data may alsoinclude the identity of and other characteristics of the patient (e.g.,social security number, date of birth, etc.), the identity of an initialuser first creating or accessing a file, and the type of study to beconducted (e.g., a pre-implantation ultrasound video acquisition study,a pre-implantation ultrasound digitization study, a pre-implantationultrasound file import study or other types of studies).Pre-implementation data may be entered by the user either directly(e.g., through a keyboard) or via pull down menus or other selectionmechanism.

[0028] In step 12, the actual patient imaging data is loaded into system100. There are various methods for accomplishing this. One method is todirectly connect processor 310 or input device 320 to an ultrasounddevice or other imaging apparatus. In this case, raw ultrasound data iscaptured in real time as the ultrasound procedure is taking place. Othermethods include entering ultrasound films or ultrasound scans into adigitizer connected to processor 310 or input device 320, or loadingimage computer files into system 100 through a disk drive or network.Other methods of loading images may also be used.

[0029] After the desired image or images have been loaded into system100, a system window 50 (as illustrated in FIG. 3) which may be providedon display device 330 displays one relatively large image scan in aworking window 52, and a plurality of other relatively smaller images inthumbnail windows 54. This layout allows the user to view multiple imagescans while designing a pre-implantation plan. In this embodiment it ispossible to store, manipulate, locate and compare different seedplacement plans as discussed in further detail below. For example,working window 52 may display a placement plan immediately underconsideration while allowing easy reference to other variationspreviously considered or to be considered via a variation selectionmenu.

[0030] At step 14, system 100 prompts the user to select a computergenerated template and position it over image scans as displayed ondisplay device 330 in order to identify predetermined structures. It isnecessary to complete template registration before it is possible tooutline structures or place seeds. Template registration ensures thatcaptured images are properly aligned with the template. Once thetemplate has been registered, the user may identify and contouranatomical structures through user interface device 350, theaforementioned templates and other available tools which function tocontour an/or outline various anatomical structures. The relevantstructures in brachytherapy treatment may include (but are not limitedto) the prostate, rectum, urethra, and bladder. System 100 supportsseveral standard templates for preoperative planning. FIG. 3 illustratesan anatomical structure 56 as outlined using user interface device 350of system 100. The structure appears as the light, somewhat circularoutline in FIG. 3.

[0031] After the anatomical structures which may impact treatment havebeen located and outlined at step 14, system 100 prompts the user toenter seed data at step 16. Seed data may include information about theseed, such as the type of radioactive material used for a seed, and theactivity of the seed material. Other seed data may also be entered.

[0032] System 100 preferably allows the user to opt for either automaticseed placement or manual seed placement in response to a query by system100 at step 18. If manual placement is selected, processing continues atstep 24, which will be described later. If automatic seed placement isselected, the system 100 allows a user to choose whether to use doseoptimization at step 20 or not. If dose optimization is selected at step20, system 100 places seeds according to various user defined criteria.These criteria may include specifying a particular dose applicable to aparticular anatomical structure or structures, such as the cancer to betreated, or the neighboring anatomical structures. If a user selectsdose optimization, the criteria are converted to an error function andan optimal plan is generated through a simulated annealing procedure. Ifa user elects not to select dose optimization at step 20, system 100 mayplace seeds in pre-programmed seed placement strategies at step 22. Suchpreprogrammed placement strategies correspond to known brachytherapymethods that create either a uniform or peripherally-weighted placementpattern. After a preprogrammed seed placement strategy has beenperformed, a user may then decide to modify the treatment at step 26 toalter the plan and selectively add, delete, move, or otherwise alterseed locations and parameters.

[0033] System 100 allows the user to alternatively manually specify seedplacement on image scans at step 24. FIG. 3 illustrates one embodimentof how an image scan might appear to a user while the user is manuallyspecifying seed locations. Seeds 58 may be located by the user onintersecting grid lines forming nodes 60 as displayed in window 52 so asto specify seed placement according to a pre-implementation plan. Afterthe user has designated the placement of a seed 58 on an image scan, auser may continue to place seeds by going back to step 24 until allseeds are located. Once the target dose value has been designated instep 16 and at least one seed has been placed in step 24, the DVH/CVA(Cumulative Dose Histogram/Contiguous Volume Analysis) plots becomeavailable for view (assuming at least one anatomical structure has beenoutlined).

[0034] As seeds are placed, system 100 preferably initiates an AnalysisProcedure at step 28 to analyze the pre-implantation plan. According tothis Analysis Procedure, the user, using user interface device 350, mayvary particular aspects of the seed placement plan with system 100providing a real-time response to the user's changes. For example,system 100 preferably displays isodose lines which illustrate the effectof the proposed treatment plan as the user modifies the plan. Theseisodose lines are displayed in working window 52 and thumbnail windows54. System 100 preferably allows the user to adjust various aspects ofthe seed placement plan including the target dose value, seed positionsand needle paths.

[0035] System 100 may also update information sections of the containedin window 50. These information sections may include the total number ofseeds designated on a particular image scan, the total number of seedsdesignated on all of the image scans or any other information relatingto the seed placement plan. The user may view a treatment program in atwo-dimensional view by designating a specific section slice to bedisplayed, or, alternatively, system 100 allows the user to view atreatment program in a three-dimensional view.

[0036] The user may also view a plan through DVH and CVA plots. A DVHdisplays a plot of the structure volume that receives a particular dose,e.g., what percentage of the volume of the structure receives a givendose of radiation. A CVA displays a plot of the homogeneity of aradiation dose rate for a target volume, e.g., what actual volume(either total or contiguous) receives a given does of radiation.

[0037] After analyzing a pre-implantation plan, the user is prompted todecide at step 40 whether the devised plan is appropriate for a patient.If the plan is not satisfactory. the user may, for example, decide toalter seed locations at step 24, or decide to alter seed data at step 16to reflect alternative seed characteristics. Other options may also beavailable to the user. Once a pre-implantation plan is selected, thetreatment plan can be implemented at step 42. Implementation of aselected plan may comprise qualified medical personnel implanting theseeds using conventional means, such as a transperineal implantationtechnique.

[0038] Pre-implantation planning may also be performed in a real-timeenvironment. Planning and evaluation may occur as the implantation isoccurring. Thus, during an implantation procedure, the user may viewinformation on display device 330. From this information, the user maythen determine whether the current seed implantation is correct andwhere to place the next seed.

[0039] Post-Implantation Evaluations

[0040] System 100 also provides a post-implantation evaluation option asillustrated by the flowchart in FIG. 4. The purpose of thepost-implantation evaluation is to allow a user to evaluate theeffectiveness of the seed placement procedure by recomputing radiationdosage levels based on actual seed placement obtained in the seedimplantation procedure. Post-implantation evaluation does differ frompre-implantation seed placement in some aspects. For example, image datafrom post-operative evaluations typically comes from CT films orstereo-shift films rather than from ultrasound images. Also, redundancycorrection techniques are typically used during post-implantationevaluation to eliminate false (duplicate) seeds from consideration. Inaddition, templates are not used during post-implantation evaluation.

[0041]FIG. 5 is an exemplary display screen which may represent thegraphical user interface presented to the user on display device 330during post-implantation evaluation. The display in FIG. 5 provides apresentation depicting the location of seeds on an image scan accordingto one embodiment of the present invention. This image scan representsactual imaging data taken from a patient following an actualimplantation procedure.

[0042] System 100 presents the user with a system window 130, whichincludes a central working window 132 and thumbnail windows 134, whichmay be presented. for example, in two columns. Working window 132includes a detailed image of a selected view while thumbnail window 134includes other images loaded into the system. A tool bar 136 portionalong the top of the display screen allows a user to manipulate data,images and system characteristics in a well known manner.

[0043] For example, pull down menus on menu bar 146 allow a user tomanipulate the system configuration through user interface device 350.In FIG. 5, menu bar 146 contains pull down menus entitled “File,”“View,” “Variations,” “Configurations.” and “Help.” The “File” menuallows a user to open and close various studies, as well as print thecurrently selected study. The “View” menu presents a user with theoptions to manipulate the view seen by the user, such as altering theshading, or enlarging or reducing the size of an image. The user mayalso interact with system 100 to select how many image scans aredisplayed in thumbnail window 134. With the “Variations” pull-down menu,a user may create new variations of a plan or evaluation, rename acurrent variation, or delete a variation. Variations (including theirpurpose, use and operation) are discussed in detail below. The“Configuration” menu allows the user to manipulate the configuration andoperation of system 100. The “Help” menu may provide information aboutsystem 100, as well as assisting the user in operating system 100.

[0044] As illustrated in FIG. 5, a toolbar 136 is located below the menubar 146 on the system window 130. The tool bar 136 contains buttonswhich perform a variety of functions, such as saving the current versionof the study, printing the current copy of the reports, enlarging animage scan, changing the canvas layout, or other controls. Other optionsmay also be available in the menu bar 146 and toolbar 136.

[0045] Patient data section 138 of system window 130 may displayinformation about a patient and a particular procedure being evaluated.This information may include the name of patient, medical history,including the treatment plan, proposed seed placement plan, the date theimplantation procedure was performed, and similar information. A systemwindow 130 may also present a user with an evaluation section 140, whichpresents summary information about the graphic display, such as targetdose and isodose mapping information. The user may evaluate an imagescan or image scans by viewing isodose lines.

[0046] If the user desires to perform a post-implantation evaluationaccording to an embodiment of the invention, system 100 will enter theimplantation evaluation at step 70 and load post-implantation data atstep 72. Post-implantation data may include the patient's medicalhistory file and raw imaging data, such as image scans, in a mannersimilar to creating a pre-implantation plan. At step 74, the useridentifies and contours anatomical structures in image scans in a mannersimilar to pre-implantation planning, so as to outline and identifymajor structures and organs. At step 76, the user enters seed data, suchas the radioactive composition of the seed and the activity level of agiven seed. At step 78, the user is prompted to identify seeds that arevisible in the image scan on display device 330 by designating a portionof an image scan using user interface device 350. This procedure issimilar to placing seeds in the pre-implantation planning, except thatseeds are identified in accordance with their actual location in theimage scan. As the user identifies the locations of various seeds,system 100 may provide an identification number for each seed. Anidentification number may, for example, be given in the order the seedsare located and identified to the system (e.g., the twelfth seed locatedis identified as seed #12, etc.). The identification numbers may be usedto later identify, the seeds for evaluation or in connection with theelimination of redundant (false) seeds.

[0047] A detailed graphical presentation of the target area andsurrounding tissue is displayed in working window 132 using falsecoloring or a gray level scale to represent tissue density or othercharacteristics provided by conventional medical imaging apparatus andsystems, such as ultrasound, CT, MRI, etc. At step 80, system 100attempts to isolate and identify structures having characteristics knownto correspond to the seeds, such as high density, high reflectivity,etc. System 100 then indicates that a structure has been tentativelyidentified as a seed by displaying an identification icon correspondingto the location of all such structures. The icon may be, for example, asmall circle positioned in the middle of the area tentatively identifiedas containing a seed.

[0048] According to an embodiment of the invention, a user may beprompted to initiate an automatic seed identification (“ASI”) process.System 100 preferably automatically identifies the location of seedsbased on image scans. The ASI process may obviate the step ofidentifying and correcting redundant seed locations.

[0049] The user is presented with a number of unidentified seeds 144shown on image scans. In one embodiment, working window 132 displays animage scan with unidentified seeds 144. A user may then locate the seedson an image scan in working window 132, as shown by identified seeds142. The user may identify, resolve, and correct redundant seedlocations. Once this is accomplished, the user may view the procedureresults according to the Analyze Procedure step (step 82) through avariety of different methods. In one method, the user may manipulateisodose lines in a similar manner to a pre-implantation procedure. Alsoa user may view a plan in a two-dimensional view, while another optionallows a user to view a plan in a three-dimensional view. Similarly, theuser may view the results through DVH and/or CVA plots. The DVH plotsand CVA plots are similar to those viewed in the pre-implantationplanning.

[0050] Multiple Variations

[0051] According to one particular aspect of the invention, the user maycreate multiple variations of pre-implantation plans and/orpost-implantation evaluations. Using multiple variations, the user maywork with a number of pre-implantation plans and/or post-implantationevaluations and individually store each plan for later retrieval andreview. In this manner, for example, a user could create severalversions of a pre-operative plan, each with a different number of seeds,different seed placement method, different seed activity level and evendifferent isotopes. The target dose and isodose contours may also bevaried among different versions. In the post-implantation evaluationmode and as another example, the user could perform one redundancycorrection where redundant seeds are deleted, and another redundancycorrection where redundant seeds are merged. The stored evaluations inthis case could later be compared to select the best fit.

[0052] In a preferred embodiment, when certain specified parameters in adefault version or in a variation are changed, the change is propagatedto all other variations in that study. For example, a change in whatcolors are assigned to associated attributes might be propagated.Additionally, an addition or deletion of a structure outline from a scanto one variation might be applied to all other variations automatically.In contrast, other parameters might be identified as variation specific.For example, each of the following parameters might be selected asvariation specific:

[0053] Target Dose; Isotope; Activity Level; Seed Positioning;Anisotropy Correction Status; and Isodose Levels.

[0054] The particular parameters which are variation specific versusthose that should be propagated may be set by the user using, forexample, a pull down menu, or, alternatively, this configuration may beprovided at install time or by a system administrator.

[0055] A pull-down menu 170 for working with variations may be presentedto the user, as illustrated by way of example in FIG. 6. A user maycreate a new variation 172, rename a variation 174, or delete avariation 176. Pull-down menu 170 may also identify the variation 178currently being used and/or others which have recently been accessed.

[0056] When creating a new variation, a user is presented with a newvariation dialog box 180, as illustrated in FIG. 7. The name 182 of thenew variation to be created may be entered using user interface device350 (i.e., keyboard to enter data; mouse to select menu items), and inone embodiment of the invention, various options regarding a newvariation may be presented to the user. For example, the user may save avariation in its current state while creating a new variation, based onthe current state of the previous variation. The new variation divergesfrom the previous variation once the user begins to make changes to thenew variation.

[0057] A user may also change the name of a variation. As shown in FIG.8, a rename variation dialog box 190 is presented to a user. A userenters a new name 192 for the variation, and activates the renamevariation function, thereby excepting the new name. A user may alsodelete a variation be activating the delete variation function 176 (FIG.6).

[0058] The system of the present invention allows a user to move easilybetween a number of variations of pre-implantation plans orpost-implantation evaluations. Thus, for example, a user could create anoriginal pre-implantation plan using specific values and placements forvarious seed. The user could then create a variation on the originalpre-implantation plan and vary either the seed values, or the seedpositions, or both and then compare the variations. This comparisonallows the user to determine which plan better meets the treatment goalsand objectives for the patient. If desired, the user may create morepre-implantation variations (as many as desired up to the resourcelimits of system 100). varying different parameters and then comparingthe different variations.

[0059] In a preferred embodiment of the present invention, system 100allows a user, when creating a new variation, to choose which state toleave current variation in when system 100 creates a new variation. Theuser may either (i) store the changes in the current variation andcreate a new variation with those changes or (ii) create a new variationbased upon the current changes to the current variation. According to apreferred embodiment, the state of the new variation is the same witheither choice. The difference is in the state of the previously currentvariation. If the first option is selected, system 100 saves the currentversion in its current state and creates a new variation. At thatmoment, the two variations are identical. They diverge when chances aremade to the new variation. If the second option is selected, system 100creates a new version as it exists at that moment and leaves thepreviously current version in its state when it was last saved. Anychanges to the previously current version since it was last saved arenot saved with respect to the previously current version. This optiontherefore allows the user to decide after one or more variation specificchanges have been made that they should be stored in the new variationbut not in the previously current variation.

[0060] Variations may be renamed, deleted and added as desired by theuser. When a variation is deleted, the first (default) variationpreferably replaces the deleted variation in window 52 or window 132 asappropriate.

[0061] Although the invention has been described in the context oftreating prostate cancer in humans, it is equally applicable totreatment plans and implementations in a wide range of human and animalprocedures and to other imaging systems used to plan, assist, monitorand confirm the placement of objects within a body. These and otherembodiments and uses of the invention will be apparent to those skilledin the art from consideration of the specification and practice of theinvention disclosed herein. The specification and examples should beconsidered exemplary only. The scope of the invention is only limited bythe claims appended hereto.

What is claimed is:
 1. In a computer implemented system for assisting inan interstitial radiation therapy treatment where the computer receivestwo-dimensional images of a three-dimensional treatment area and thecomputer system comprises a display for graphically displaying thetwo-dimensional images, and a processor for creating interstitialradiation therapy treatment plans, a method comprising the steps of:providing variation specific parameters; creating an original plan usingvariation specific parameters; creating a variation plan by manipulatingvariation specific parameters of the original plan; and displaying theoriginal plan and the variation plan on the display, wherein theoriginal plan and the variation plan are mutually accessible forcomparison on the display.
 2. The method according to claim 1, whereinthe step of creating the variation plan further comprises: (a) savingthe original plan; (b) manipulating variation specific parameters of theoriginal plan; and (c) creating a variation plan; and the step ofdisplaying further comprises displaying the saved original plan and thevariation plan.
 3. The method according to claim 2, wherein variationspecific parameters comprise at least one of: a. a target dosage; b. aradiation source type; c. a radiation source activity level; d.radiation source positioning; e. an anisotropy correction constant; f. alist of isodose values for two-dimensional display; and g. an isodoselevel for three-dimensional display.
 4. The method according to claim 1,wherein the step of creating the variation plan further comprises: (a)saving the original plan; (b) creating a variation plan, where thevariation plan is identical to the original plan; and (c) manipulatingvariation specific parameters of the variation plan; and the step ofdisplaying further comprises displaying the saved original plan and themanipulated variation plan.
 5. The method according to claim 4, whereinvariation specific parameters comprise at least one of: a. a targetdosage; b. a radiation source type; c. a radiation source activitylevel; d. radiation source positioning; e. an anisotropy correctionconstant; f. a list of isodose values for two-dimensional; and g. anisodose level for three-dimensional display.
 6. The method according toclaim 1, further comprising the steps of: saving at least one of theoriginal plan and the variation plan.
 7. The method according to claim1, further comprising the step of: recalling a saved plan, wherein thesaved plan is one of a saved original plan and a saved variation plan;and comparing the saved plan to the other of the variation plan or theoriginal plan.
 8. The method according to claim 1, further comprisingthe step of designating the variation specific parameters.
 9. In acomputer implemented system for assisting in an interstitial radiationtherapy treatment, where the computer receives two-dimensional images ofa three-dimensional treatment area and the computer system comprises adisplay for graphically displaying the two-dimensional images, and aprocessor for creating interstitial radiation therapy treatmentevaluations of the treatment area, a method comprising the steps of:providing variation specific parameters; creating an original evaluationusing variation specific parameters; creating a variation evaluation bymanipulating variation specific parameters of the original evaluation;and displaying the original evaluation and the variation evaluation onthe display, wherein the original evaluation and the variationevaluation are mutually accessible for comparison on the display. 10.The method according to claim 9, wherein the step of creating thevariation evaluation further comprises: (a) saving the originalevaluation; (b) manipulating variation specific parameters of theoriginal evaluation; and (c) creating a variation evaluation; and thestep of displaying further comprises displaying the saved originalevaluation and the variation evaluation.
 11. The method according toclaim 10, wherein variation specific parameters comprise at least oneof: a. a target dosage; b. a radiation source type; c. a radiationsource activity level; d. radiation source positioning; e. an anisotropycorrection constant; f. a list of isodose values for two-dimensionaldisplay; and g. an isodose level for three-dimensional display.
 12. Themethod according to claim 9, wherein the step of creating the variationevaluation further comprises: (a) saving the original evaluation; (b)creating a variation evaluation, where the variation evaluation isidentical to the original evaluation; and (c) manipulating variationspecific parameters of the variation evaluation; and the step ofdisplaying further comprises displaying the saved original evaluationand the manipulated variation evaluation.
 13. The method according toclaim 12, wherein variation specific parameters comprise at least oneof: a. a target dosage; b. a radiation source type; c. a radiationsource activity level; d. radiation source positioning; e. an anisotropycorrection constant; f. a list of isodose values for two-dimensionaldisplay; and g. an isodose level for three-dimensional display.
 14. Themethod according to claim 10, further comprising the steps of: savingsat least one of the original evaluation and the variation evaluation.15. The method according to claim 10, further comprising the step of:recalling a saved evaluation, wherein the saved evaluation is one of asaved original evaluation and a saved variation evaluation; andcomparing the saved evaluation the other of the variation evaluation orthe original evaluation.
 16. The method according to claim 9, furthercomprising the step of designating the variation specific parameters.17. A computer implemented system for assisting in an interstitialradiation therapy treatment, the system comprising: means for receivinga plurality of two-dimensional images of a three-dimensional treatmentarea: means for providing variation specific parameters; means forcreating an original interstitial radiation therapy treatment plan inthe treatment area using variation specific parameters; means forcreating a variation plan by manipulating variation specific parametersof the original plan; and means for displaying the original plan and thevariation plan, wherein the original plan and the variation plan aremutually accessible for comparison on the display means.
 18. The systemaccording to claim 17, wherein creating the variation plan furthercomprises: (a) saving the original plan; (b) manipulating variationspecific parameters of the original plan; and (c) creating a variationplan; and displaying further comprises displaying the saved originalplan and the variation plan.
 19. The system according to claim 18,wherein variation specific parameters comprise at least one of: a. atarget dosage; b. a radiation source type; c. a radiation sourceactivity level; d. radiation source positioning; e. an anisotropycorrection constant; f. a list of isodose values for two-dimensionaldisplay; and g. an isodose level for three-dimensional display.
 20. Thesystem according to claim 17, wherein creating the variation planfurther comprises: (a) saving the original plan; (b) creating avariation plan, where the variation plan is identical to the originalplan; and (c) manipulating variation specific parameters of thevariation plan; and displaying further comprises displaying the savedoriginal plan and the manipulated variation plan.
 21. The systemaccording to claim 20, wherein variation specific parameters comprise atleast one of: a. a target dosage; b. a radiation source type; c. aradiation source activity level; d. radiation source positioning; e. ananisotropy correction constant; f. a list of isodose values fortwo-dimensional display; and g. an isodose level for three-dimensional.22. The system according to claim 17, further comprising: means forsaving at least one of the original plan and the variation plan.
 23. Thesystem according to claim 17, further comprising: means for recalling asaved plan, wherein the saved plan is one of a saved original plan and asaved variation plan; and means for comparing the saved plan to theother of the variation plan or the original plan.
 24. The methodaccording to claim 17, further comprising the step of designating thevariation specific parameters.
 25. A computer implemented system forassisting in an interstitial radiation therapy treatment, the systemcomprising: means for receiving a plurality of two-dimensional images ofa three-dimensional treatment area; means for providing variationspecific parameters; means for creating an original interstitialradiation therapy treatment evaluation in the treatment area usingvariation specific parameters; means for creating a variation evaluationby manipulating variation specific parameters of the originalevaluation; and means for displaying the original evaluation and thevariation evaluation, wherein the original evaluation and the variationevaluation are mutually accessible for comparison on the display means.26. The system according to claim 25, wherein creating the variationevaluation further comprises: (a) saving the original evaluation; (b)manipulating variation specific parameters of the original evaluation;and (c) creating a variation evaluation; and displaying furthercomprises displaying the saved original evaluation and the variationevaluation.
 30. The system according to claim 26 wherein variationspecific parameters comprise at least one of: a. a target dosage; b. aradiation source type; c. a radiation source activity level; d.radiation source positioning; e. an anisotropy correction constant; f. alist of isodose values for two-dimensional display; and g. an isodoselevel for three-dimensional display.
 28. The system according to claim25, wherein creating the variation evaluation further comprises: (a)saving the original evaluation; (b) creating a variation evaluation,where the variation evaluation is identical to the original evaluation;and (c) manipulating variation specific parameters of the variationevaluation; and displaying further comprises displaying the savedoriginal evaluation and the manipulated variation evaluation.
 29. Thesystem according to claim 28, wherein variation specific parameterscomprise at least one of: a. a target dosage; b. a radiation sourcetype; c. a radiation source activity level; d. radiation sourcepositioning; e. an anisotropy correction constant; f. a list of isodosevalues for two-dimensional display; and g. an isodose level forthree-dimensional display.
 30. The system according to claim 25, furthercomprising: means for saving at least one of the original evaluation andthe variation evaluation.
 31. The system according to claim 25, furthercomprising: means for recalling a saved evaluation, wherein the savedplan is one of a saved original evaluation and a saved variationevaluation; and means for comparing the saved evaluation to the other ofthe variation evaluation or the original evaluation.
 32. The methodaccording to claim 25, further comprising the step of designating thevariation specific parameters.